The overall objectives of the proposed research are: (1) to study the growth regulation of normal versus tumor intestinal cells in vitro. These studies will focus on the effects of various hormones (Hydrocortisone, thyroxin, glucagon, insulin, gastrin, etc.) and of an apparently specific growth inhibitor partially purified from intestinal villous cells on normal intestinal epithelial cells and on tumor cell lines derived from dimethylhydrazine-induced tumors of the small and large intestine. (2) To study the susceptibility to chemical carcinogenesis of normal epithelial cells derived from different portions of the rat intestine. Malignant transformation will be induced by addition of various chemicals (benzo(a)pyrene, 1, 2-dimethylbenz (a) anthracene, methylnitrosourea and N-methyl-N'-nitro-N-nitrosoguanidine) and monitored by following many possible cellular changes (a different morphology, increased saturation density, growth in soft agar, plasminogen activator production, decreased fibronectin deposition). (3) To attempt to establish normal epithelial cell lines from human small intestine; if obtained, these cell lines will be characterized by morphologic and immunologic criteria similar to our studies of rat intestinal cells.